A checkpoint control orchestrates the replication of the two chromosomes of Vibrio cholerae

International audienceBacteria with multiple chromosomes represent up to 10% of all bacterial species. Unlike eukaryotes, these bacteria use chromosome-specific initiators for their replication. In all cases investigated, the machineries for secondary chromosome replication initiation are of plasmid origin. One of the important differences between plasmids and chromosomes is that the latter replicate during a defined period of the cell cycle, ensuring a single round of replication per cell. Vibrio cholerae carries two circular chromosomes, Chr1 and Chr2, which are replicated in a well-orchestrated manner with the cell cycle and coordinated in such a way that replication termination occurs at the same time. However, the mechanism coordinating this synchrony remains speculative. We investigated this mechanism and revealed that initiation of Chr2 replication is triggered by the replication of a 150-bp locus positioned on Chr1, called crtS. This crtS replication-mediated Chr2 replication initiation mechanism explains how the two chromosomes communicate to coordinate their replication. Our study reveals a new checkpoint control mechanism in bacteria, and highlights possible functional interactions mediated by contacts between two chromosomes, an unprecedented observation in bacteria

Consolidation of Spray-Dried Amorphous Calcium Phosphate by Ultrafast Compression: Chemical and Structural Overview

A large amount of research in orthopedic and maxillofacial domains is dedicated to the development of bioactive 3D scaffolds. This includes the search for highly resorbable compounds, capable of triggering cell activity and favoring bone regeneration. Considering the phosphocalcic nature of bone mineral, these aims can be achieved by the choice of amorphous calcium phosphates (ACPs). Because of their metastable property, these compounds are however to-date seldom used in bulk form. In this work, we used a non-conventional “cold sintering” approach based on ultrafast low-pressure RT compaction to successfully consolidate ACP pellets while preserving their amorphous nature (XRD). Complementary spectroscopic analyses (FTIR, Raman, solid-state NMR) and thermal analyses showed that the starting powder underwent slight physicochemical modifications, with a partial loss of water and local change in the HPO42- ion environment. The creation of an open porous structure, which is especially adapted for non-load bearing bone defects, was also observed. Moreover, the pellets obtained exhibited sufficient mechanical resistance allowing for manipulation, surgical placement and eventual cutting/reshaping in the operation room. Three-dimensional porous scaffolds of cold-sintered reactive ACP, fabricated through this low-energy, ultrafast consolidation process, show promise toward the development of highly bioactive and tailorable biomaterials for bone regeneration, also permitting combinations with various thermosensitive drugs

Sacerdoce de tous les chrétiens et sacerdoce ministériel dans la théologie de théodulphe d Orléans

El artículo presenta la forma en que Teodulfo de Orleans, clérigo carolingio de origen visigodo, soluciona la contradicción existente entre el sacerdocio universal y el sacerdocio sacerdotal. Su respuesta consiste en reconocer ambas formas de sacerdocio pero atribuyendo a cada uno características específicas. De esta manera no contradice los textos escriturarios pero mantiene y acentúa la distinción entre un orden clerical y otro laico.Fil: Hernandez Rodriguez, Alfonso Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Saavedra 15. Instituto Multidisciplinario de Historia y Ciencias Humanas; Argentin

Le marketing du livre : quand le nom de l'auteur devient une marque : la cas de la littérature

Science politiqueCe mémoire se fixe pour objectif de présenter les particularités du marketing de l'édition et tente de répondre à la problématique suivante:peut-on considérer un auteur comme une marque? Une présentation du paysage éditorial français, et particulièrement de ses logiques économiques, constitue la première partie de ce travail.Les spécificités du marketing du livre et du concept de 'marque-auteur' sont évoqués dans une deuxième partie. Enfin, il sera question de la 'marque-auteur' vue sous l'angle de l'éditeur, du lecteur ainsi que de la perennité de ce concept

Une première description du projet drones et intelligence ambiante

Journée tenue à Bruz - France. Le document est constitué de 2 pages.Journée thématique Réseaux au CELAR 2008Une première description du projet drones et intelligence ambiant

Secure cooperative ad hoc applications within UAV fleets -- Position paper --

International audienceA proper situation management system is one of the keys to success on the battlefield. It strongly relies on data collection, fusion and interpretation. Unmanned Aerial Vehicles (UAVs) are becoming a major collection platform, but there is almost no collaborative intelligence in these systems. We claim that a swarm of small UAVs connected together that could make cooperative decisions in an autonomous way (without requiring any intervention from the ground) would be a major contributor to the information superiority. In this paper we present our vision of this approach and the research project that we are running to achieve an operational system. It deals with levels 1, 2 and 4 of the DoD JDL definition of information fusion. This is a position paper describing a work in progress

Silent Mischief: Bacteriophage Mu Insertions Contaminate Products of Escherichia coli Random Mutagenesis Performed Using Suicidal Transposon Delivery Plasmids Mobilized by Broad-Host-Range RP4 Conjugative Machinery ▿

Random transposon mutagenesis is the strategy of choice for associating a phenotype with its unknown genetic determinants. It is generally performed by mobilization of a conditionally replicating vector delivering transposons to recipient cells using broad-host-range RP4 conjugative machinery carried by the donor strain. In the present study, we demonstrate that bacteriophage Mu, which was deliberately introduced during the original construction of the widely used donor strains SM10 λpir and S17-1 λpir, is silently transferred to Escherichia coli recipient cells at high frequency, both by hfr and by release of Mu particles by the donor strain. Our findings suggest that bacteriophage Mu could have contaminated many random-mutagenesis experiments performed on Mu-sensitive species with these popular donor strains, leading to potential misinterpretation of the transposon mutant phenotype and therefore perturbing analysis of mutant screens. To circumvent this problem, we precisely mapped Mu insertions in SM10 λpir and S17-1 λpir and constructed a new Mu-free donor strain, MFDpir, harboring stable hfr-deficient RP4 conjugative functions and sustaining replication of Π-dependent suicide vectors. This strain can therefore be used with most of the available transposon-delivering plasmids and should enable more efficient and easy-to-analyze mutant hunts in E. coli and other Mu-sensitive RP4 host bacteria

Squelettisation par blocs pour des grands volumes de données 3D: application à la microcirculation cérébrale

National audienceno abstrac